Powered roller conveyors, commonly referred to as a "live" roller conveyor, have been utilized extensively for many years to permit transporting of articles within warehouses, factories or the like. These known conveyors, in order to permit powered rotation of the conveyor rollers, have generally utilized complex and costly driving mechanisms in order to permit powered rotation of the conveyor rollers throughout the rather substantial length of the conveyor. For example, many known conveyors of this type have utilized extremely long power transmission devices employing gears and/or belts for joining the rollers together in a powered relationship. These mechanisms have been necessarily complex and hence costly, and have also involved substantial maintenance and repair, particularly when systems employing belts are utilized. In addition, power driving arrangements of this type are more difficult to control, particularly when it is desired to divide the conveyor into a plurality of longitudinallly aligned zones which can be individually controlled and driven so as to permit accumulation of goods on the conveyor.
In an attempt to improve the driving of the conveyor rollers, many conveyor systems have adopted the use of a drive shaft which extends longitudinally of the conveyor and is then drivingly interconnected to the conveyor rollers through a plurality of intermediate power transmitting mechanisms. This longitudinally extending power shaft, conventionally referred to as "line shaft", has permitted some simplification in the driving mechanism for the conveyor, and in particular has permitted more desirable control over the zones of the conveyor. One such system employing a "line shaft" drive is illustrated in U.S. Pat. No. 3,696,912. This system, which is typical of known powered roller conveyors employing a line shaft, utilizes a plurality of twisted belts which extend between the line shaft and the conveyor roller shafts. The use of a plurality of twisted belts for individually driving the rollers, or zones of rollers, has worked successfully except that these belts are subject to substantial wear and breakage under certain conditions, so that maintenance and repair of conveyors employing this type of drive has necessarily been substantial. In addition, conveyors of this general type also normally require that a shiftable clutch be provided between the conveyor roller and a coaxial pulley member which is driven by the belt in order to permit zoning and hence stopping of the selected conveyor rollers when desired. This further increases both the structural and the operational complexity of the drive and control systems.
While conveyors employing a line shaft and twisted belts, as described above, have operated in a more desirable manner than the powered conveyor rollers previously known, and hence have met with substantial commercial success, nevertheless this type of powered roller conveyor still possesses features which have made its usage less than desirable. For example, the required frequency of maintenance and repair on conveyors of this type is higher than desired under some operating conditions. Further, the individual belt-type drive mechanism which joins the conveyor rollers to the line shaft possesses undesired structural and mechanical complexities which increase the overall cost of the conveyor system. Further, zoning of conveyors of this type, so as to permit zero pressure accumulation of articles thereon, requires a complex control structure which must be associated with all of the intermediate belt-type drive mechanisms located within each zone. These conveyors also require the use of grooved driving and driven pulleys for engagement with the twisted belt, thereby increasing the number of components and hence the overall complexity of the driving system.
In an effort to improve upon powered roller conveyors of the above-described type, a further powered roller conveyor has recently been commercially introduced which employs a line shaft extending longitudinally of the conveyor. In this case, however, the driving torque is transmitted from the line shaft to the conveyor rollers through a plurality of intermediate driving mechanisms which employ a plurality of friction rollers. One of these intermediate driving mechanisms is drivingly connected between the line shaft and each zone of the conveyor. This intermediate driving mechanism, however, is structurally complex and hence undesirable due not only to the large number of friction drive rollers employed for transmitting torque between the line shaft and one of the conveyor rollers, but due also to the bulkiness and hence the space required for this intermediate driving mechanism. This intermediate driving mechanism normally utilizes a pair of coaxially and rigidly connected friction drive rollers. One of these coaxially aligned rollers is frictionally driven from the line shaft, and the other frictionally drives a third friction drive roller which is disposed in parallel with the conveyor roller, which third friction drive roller in turn is in driving engagement with one of the conveyor rollers. The remaining conveyor rollers within the zone are in turn drivingly connected in series to the said one conveyor roller by means of intermediate friction drive rollers so as to permit all of the conveyor rollers in the zone to be rotationally driven.
Thus, the driving arrangement of the above-described conveyor is undesirable due not only to the large number of parts involved in the intermediate driving mechanism, but due also to the necessity of having to utilize additional intermediate friction drive rollers in order to serially drivingly connect the other conveyor rollers within the zone. This additionally increases the complexity of the driving mechanism, and increases the possibility of slippage between the different conveyor rollers. A further disadvantage of this arrangement is that the intermediate driving mechanism, even though drivingly connected directly to only a single conveyor roller, must be capable of transmitting sufficient torque to permit driving of all of the conveyor rollers within the zone. This requires that the friction torque transmitting capability of the intermediate driving mechanism be of substantially greater capacity, which thus not only increases the size and bulkiness of the intermediate driving mechanism, but also increases the wear and slippage of the system.
A further disadvantage of the driving arrangement associated with the above-described conveyor relates to the manner in which the line shaft is associated with the conveyor. While the line shaft does extend longitudinally of the conveyor, nevertheless the line shaft is broken up into a plurality of shaft segments which are substantially coaxially aligned and extend in the longitudinal direction of the conveyor. Each shaft segment, as associated with a conveyor zone, has its own control structure associated therewith so that each shaft segment is individually rotatably driven or stopped in order to permit control over the associated conveyor rollers. In this way, zoning of the conveyor in order to achieve zero presure accumulation of articles thereon is achieved. This overall structure, and particularly the control system therefor, is obviously undesirably complex.
Accordingly, it is an object of the present invention to provide an improved powered roller conveyor which utilizes a line shaft drive, and which overcomes the many disadvantages associated with known powered roller conveyors as explained above. More specifically, it is an object of the present invention to provide:
1. A powered roller conveyor which utilizes a rotatable line shaft which extends longitudinally of the conveyor for causing powered rotation of the conveyor rollers, which line shaft extends substantially continuously in the longitudinal direction of the conveyor and can be substantially continuously driven so as to simplify the control therefor.
2. A conveyor, as aforesaid, which utilizes an extremely simple intermediate driving mechanism connected between the line shaft and the individual conveyor rollers for permitting direct driving of each conveyor roller.
3. A conveyor, as aforesaid, wherein the intermediate driving mechanism preferably employs a single friction drive roller which drivingly connects between a conveyor roller and the line shaft for permitting transmission of rotational driving torque therebetween.
4. A conveyor, as aforesaid, wherein the line shaft preferably incorporates thereon shiftable sleeves which can be axially shifted into frictional engagement with the intermediate driving roller when transmission of rotational driving torque from the line shaft to the conveyor roller is desired.
5. A conveyor, as aforesaid, which can be easily divided into a plurality of individually controlled zones so as to permit zero pressure accumulation of articles on the conveyor.
6. A conveyor, as aforesaid, wherein the plurality of shiftable sleeves as mounted on the line shaft can be jointly controlled to permit the respective zone of the conveyor to be shifted into a disengaged condition wherein the respective intermediate driving mechanisms are deenergized when stoppage of the respective conveyor zone is desired.
7. A conveyor, as aforesaid, wherein the intermediate driving mechanism is small in size, inexpensive to manufacture and install, and durable in operation.
8. A conveyor, as aforesaid, wherein the intermediate driving mechanism permits direct driving of each conveyor roller so that an intermediate driving mechanism is thus associated with each single or adjacent pair of conveyor rollers, whereby a minimal torque is transmitted through the intermediate driving mechanism.
9. A conveyor, as aforesaid, wherein the improved powered driving arrangement is desirable for use in not only a straight conveyor section, but is also highly desirable for providing powered rotation of the rollers throughout a curved conveyor section.
10. A conveyor, as aforesaid, wherein a line shaft section also extends longitudinally of the curved conveyor section and is frictionally drivingly connected to the individual conveyor rollers by a plurality of said intermediate driving mechanisms, which mechanisms in the curve conveyor section are substantially identical to the driving mechanisms in the straight conveyor sections.
Other objects and purposes of the invention will be apparent to persons familiar with structures of this general type upon reading the following specification and inspecting the accompanying drawings.